The invention relates generally to an air suspension system for a motor vehicle and more particularly to an air suspension system having both a load-leveling capability and a kneeling capability.
In the past air suspension systems for motor vehicles incorporating a leveling mechanism automatically maintaining a predetermined relationship between the vehicle chassis and the road wheels have been well known. These air suspension systems are primarily designed around the load-leveling valve. Some of these load-leveling valves incorporate a safety feature so that the air in the air spring will be maintained even though a leak develops in another part of the system. An example of this type of an air suspension system is illustrated in U.S. Pat. No. 3,037,788.
One of the problems that has existed with air suspension systems having a single load-leveling valve to control both the front air springs of the vehicle has been that there was usually a common conduit between the two front air springs resulting in free fluid communication therebetween. In instances where there was a heavy impact on, for instance, the near-side spring would cause a surge of fluid into the off-side spring and any rolling tendancy of the vehicle due to the impact on the near-side was accentuated by a volumetric increase in the off-side spring and an uncontrollable or uncomfortable roll developed. In order to overcome this problem isolation valves were developed such as illustrated in U.S. Pat. No. 2,949,316.
In the past air suspension systems capable of kneeling the front end of a vehicle have been known. These air suspension systems however position the valves for kneeling the vehicle in series with the load-leveling valve of the air suspension systems and have not proven entirely satisfactory.
It is an object of the invention to provide a novel air suspension system for a vehicle having both a load-leveling capability and a front end kneeling capability.
It is also an object of the invention to provide a novel air suspension system for a vehicle having a load-leveling valve in a fluid circuit separate from that of the fluid circuit containing the front end kneeling valves.
It is also an object of the invention to provide a novel air suspension system for a vehicle having an isolation valve in series with a load-leveling valve in which the isolation valve is also in the fluid flow path between the laterally spaced front air springs of the vehicle.
It is another object of the invention to provide a novel air suspension system for a vehicle having a minimal number of valves in the system and having the valves of the most economical variety.
It is a further object of the invention to provide a novel air suspension system for a vehicle having the capability of varying the time required to kneel the front end of the vehicle and also to raise it up to a desired travelling height.